Modified polymers that are modified by various nitrones have been known conventionally as polymers contained in rubber compositions for use in tires and the like (see, e.g., Japanese Examined Patent Application Publication No. S47-25712A, and Japanese Unexamined Patent Application Publication Nos. S48-16996A and 2007-70439A).
The present inventors have found that, even though cases where a modified polymer that is modified with a nitrone having a carboxy group enhances the value of tan δ (60° C.), and even though cases where a modified polymer that is modified with a nitrone having no carboxy group (e.g. diphenylnitrone) enhances the value of tan δ (0° C.), compared to a case where an unmodified polymer is used, tensile properties such as tensile strength (TB) and/or elongation at break (EB) are significantly lowered in both the cases.
Note that tan δ (0° C.) and tan δ (60° C.), which are loss tangents (loss factors), are known as an indicator of wet grip performance and an indicator of rolling resistance, respectively.